2001 Durango 5.9
129K
When I bought it I had to replace head gaskets and also 1 cracked piston. During rebuild I replaced all rod bearings.
Have about 1K of miles on it. Now when I start I have a oil pressure of almost mid guage but after the car warms up the oil pressure will drop all the way to bottom and the check guage light comes on.
Let engine cool and pulled oil pressure sending unit and put in a manual pressure gauge. Start up I have just over 40 PSI gauge. After I get engine warn the pressure will drop below 10 PSI guage.
I know I did not replace the main or cam bearings. Don't recall if I replaced oil pump-will do record check.
Any thoughts.
Sure hate to pull that monster again.
Thanks

 

Could be the main bearings but I would have thought it was the rods. I would replace the PCV Valve and a possible oil pump. It could be a clogged pick up sceen on the oil pump.

 

Are these pressures at idle or at higher RPMs. My guess would be oil pump.

 

The low pressure is at idle after engine is hot-as I raise engine rpm the oil pressure will go up to about 35-40.
Tks

 

Well I changed oil and filter today. I used 20 -50 oil-something I've never done but wanted to see the results.
Initial start I have just over 60 PSIG, as the engine temp goes up the pressure goes down. When the temp is in the center of the guage the pressure is about 12 PSIG, at idle of 600RPM, raised to 1500rpm and pressure is 35, at 2000 RPM pressure is 45.

My records do not show I replaced the oil pump during the rod bearing replacement, and I don't remember. I understand oil will thin with increase of temp. Don't see how it could be oil pick up screen and now doubt it is oil pump--but not sure.

Looking today I think I might be able to lift engine up enough to remove oil pan and put in a high volume pump--50 bucks and some labor-worth a try I guess.
If it comes to a complete removal I may just take to local auction.
Thanks all

 

While you have it off you need to plastigauge the bearings to crank shaft to ensure you didn't use too small of bearings.


In fact did you plastigauge the bearings BEFORE you finished install or did you just install what ever bearings the auto parts store told you?

 

if you are using 20w50 oil you are using the wrong weight of oil for your engine, iirc 10w30 is what these trucks use

 

He knows this, the OP stated he tried it to help him narrow down the problem. If it's a bearing issue then the thicker oil would be harder to push through so he would get and increase in oil pressure which it looks like he got. Thats the reason I asked him to provide the plastigauge measurement or if he even did it. If the bearings are too small then he would have low oil pressure.

 

Thanks Hydra- I wanted to post a simular reply but didn't want to start a flame war.
As for the plastigauge--I did not --my bad. While I had heads at shop being checked I already had block on my eng stand. So I pulled rodbearings and although they looked good I went ahead and replaced them. However I looked at main but did not replace. Yes I know I don't have calibraded eyes!
At least it is not my main vehicle, in fact the main use is to transport my two over weight boxer dogs around--they love the rear area and AC.
I still have my trusty 02, 2550 Ram with a whole 90 K on it.

I'll just tuff it up and pull it again.
I will do it right this time and use the platigauge on rods and mains. However what is best way to ck cam bearings?

Thanks all

 

sorry bout that, must have missed part of it and jumped on the part i noticed as wrong . . . (my bad)